Messages in this thread | | | From | Valentin Schneider <> | Subject | Re: [PATCH 2/2] sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans multiple LLCs | Date | Thu, 09 Dec 2021 14:23:40 +0000 |
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On 06/12/21 15:12, Mel Gorman wrote: > Gautham had similar reasoning to calculate the imbalance at each > higher-level domain instead of using a static value throughout and > it does make sense. For each level and splitting the imbalance between > two domains, this works out as > > > /* > * Calculate an allowed NUMA imbalance such that LLCs do not get > * imbalanced. > */ > for_each_cpu(i, cpu_map) { > for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) { > struct sched_domain *child = sd->child; > > if (!(sd->flags & SD_SHARE_PKG_RESOURCES) && child && > (child->flags & SD_SHARE_PKG_RESOURCES)) { > struct sched_domain *top = sd; > unsigned int llc_sq; > > /* > * nr_llcs = (top->span_weight / llc_weight); > * imb = (child_weight / nr_llcs) >> 1 > * > * is equivalent to > * > * imb = (llc_weight^2 / top->span_weight) >> 1 > * > */ > llc_sq = child->span_weight * child->span_weight; > while (top) { > top->imb_numa_nr = max(1U, > (llc_sq / top->span_weight) >> 1); > top = top->parent; > } > > break; > } > } > } >
IIRC Peter suggested punting that logic to before domains get degenerated, but I don't see how that helps here. If you just want to grab the LLC domain (aka highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES)) and compare its span with that of its parents, that can happen after the degeneration, no?
> I'll test this and should have results tomorrow. > > -- > Mel Gorman > SUSE Labs
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